1. Field of the Invention
This invention relates to a pile driving and pile removing method and more particularly to such a method in which the resistance at the time of pile driving or pile removing is reduced by causing a chemical agent to be present on the pile surface or in the vicinity thereof.
2. Description of the Background Art
As conventional methods for reducing resistance at the time of driving/removing a steel pipe pile or the like into/from the ground, it has been known to spray water onto the pile surface or, during pile driving, to jet water into the ground from a jet pipe attached to the tip of the pile.
These methods are sometimes difficult to implement because it may be hard to secure the large amounts of water required and, when the water is available, the ground may be weakened by the large quantity of water injected.
Further, dirt may adhere to the web of the pile during removal so that a hole remains in the ground after the pile is extracted. This amounts to a form of secondary environmental pollution.
On the other hand, in the shielded pile driving method it is known to use a chemical agent for reducing the frictional resistance at the outer surface of the tunneling pipe. The liquid substance used is, as disclosed for example in Japanese Patent Public Disclosure No. 58(1983)-27774, initially a water absorbent high polymer in the form of dry spheres. Injection of the agent at time of pile driving is thus troublesome. The injected agent absorbs water and becomes a gel, but the time required for this reaction is disadvantageously long.